Telephone apparatus



J. F. TOOMEY.

TELEPHONE APPARATUS.

APPLICATION FILED MAY I6, 1919.

1 YQAWHW,

KNVENTOYR Jliolmy BY ATTORNEY Patented Feb. 21, 19 22.

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xi '1 Y 1. s I 6 a is o r. 3 me i. i h as" i i his o 358313.221, N."51".. AfifiIGNGR 'lO AMERICAN TEIiEIPEZGEilE AND 46 one 9 s Applicationfiled. na 1e,

the receiving on telephone circuits and the arrangements are intendedparticularly to be used at substations where the subscribers are unableto hear properly with the usual substation apparatusor Where othercircumstances make it especially desirable to nu p is required.

prove receiving.

in general an improvement in receiving may be ei fected by connecting atelephone repeater amplifier in the receiving circuit at the substation,so arranged that it will amplify the voice currents in the receivingcircuit. Where an arrangement of this kind is employed With ordinarytypes of telephone substations, the amplified currents in the receiverare of suiiicicnt magnitude under certain conditions toaidectthediaphragm of the transmitter, thereby creating a conditionknown. as singing. This feature. in addition to beingob iectionable tothe subscriber, practically makes the arrangement inoperative if anyappreciable amplification Furthermore with such an aren enient thecurrents in the receiver are of such magnitude that the subscriber couldnot speak directly into the transmitter mouthpiece without making thereceiver currents objectionably loud. Accordingly to prevent suchdiiiiculties the substation cmlodicd in the. arrangements of thisinvention'includes a side tone reduction coil of the type illustrated inthe U. 5i. Patent No.- lfil/L'T'l granted to G. A. Campbell referencebeing had to Fig. 1;. of said patent. Due to the amplification oi thereceiver current some means is desirable in this arrangement to preventobjectionable and possibly dangerous clicks in the receiver due tostatic discharges on the line or an accidental connection of ringingcurrent to the circuit whi'ie the subscriber has he receiver to his ear.in the arrangements of this invention.

AEPARATUS.

Specification of Letters Eateut. Pgieniagqi 231 @9252 1919. Serial No.297,452.

this is accomplished by including therein a bridge or shunt across theinput circuit of the repeater amplifier, the bridge including an elementsuch as carhorundurn which has the property or decreasing in resistanceWhen subjected to a sudden lllCl'afiSQ in voltage on the line.Accordingly a sudden in-. crease of voltage on the telephone circuitwould cause the bridge to operate-as a shunt for the, current. T heinvention furthermore includes means whereby the repeater amplh iier maybe switched in and out of the receiving circuit and its eflicienc'yregulated by the operator. Supervisory apparatus inlay also beassociated with the arrangements of the invention. Other and furtherfeatures of the invention will be more clear from the detaileddescription of the operation of the invention:

'- In the drawing is illustrated a circuitdiagram of a preferred form ofthe invention.

While the arrangements or the invention have been specificallyillustrated as associated with a private branch exchange. it isunderstood that it is capable of embodiment in many other forms ofcircuits. station 1 is illustrated which includes a transmitter '2, areceiver 3, and the windings i, 5 and 6 so arranged as to substantiallyreduce and prevent side tone disturbances, siniiiar arrangements beingillustrated, in the U. S. Patent No. 1.254.116 to G. A. Campbell. Thesubstation 1 is connected to the jack J at the switchboard of theprivate branch exchange operator. A. jack J is also provided for testingthe current iiow over the circuit. For this purpose a plug (not shown)would be provided which might be connected to an amulet-er and by thismeans the amount of current flowing through the repeater circuit mightbodetermincd for testing purposes. Associated with the receiver circuitis the repeater amplifier 12, which is of the type illustrated in the U.S. patents No. 1,156.636; and No. 1,159,603 to H. E. Shreeve. inrepeater 12 the repeater button is'illustrated as 13. the magnetizingwinding is 16 and is connected to the retardationccil 17. thecompensating;winding is 14*. and i5 is the receiving winding. Located atthe switchboard of the private branch exchange are the keys K K and KlVhen the key K is operated the operators supervisorv' apparatusassociated with corn ductors 28 may be connected to the receiver A. Sub-&

circuit. When the keys K, or K are operated the repeater 12 is connectedto the receiver circuit and rendered operative. The

key K furthermore controls the relay 22 and means for regulating thegain of the repeater. Bridged across the input path of the repeateris'the shunt 10 including carborundum element which will decrease inresistance when subjected to an increase in voltage. Any sudden increaseof voltage on the telephone circuit accordingly will reduce theres1stance of the shunt path 10 and the increased currents transmittedto the receiver circuit will be shunted through the path 10. By thismeans objectionable and possibly dangerous clicks in the receiver due tostatic discharges on the line or other end den increase of currentthereover are prevented.

The invention may now be more fully understood from the followingdescription of its operation.

If a connection is desired with the subtation l, the operator at. theprivate branch exchange will insert the plug of her cord circuit or ofthe calling line into the jack J. The connection will then be completedto the receiver of the substation as follows: from the tip contact ofjack J, conductor 8, winding 4, contact 34, conductors 35, 36, 87 and38, contact 70, to the receiver 3,-and also from the ring contact ofjack J over conductor 7, winding 6, conductors 39, 4:0 and 4;]. to thereceiver 3. If the operator desires to monitor or supervise such aconnec tion, the key K will be operated and the following circuitclosed: from ground, contact of key K conductor i2, winding of relay 27,to battery. The closing of this circuit will operate relay 27 andconnect the conductors 28 leadin to the operators telephone set to theconductors 40 and 41 of the above traced circuit. If it is desired toinclude in the connection therep'eater apparatus 12 either the key K orthe key K may be thrown. If the key K is thrown, the following circuitwill be closed: from round, contact of jack J, upper contact of rey Kconductor 42, winding oi relay 9, conductor 13, winding of relay 26,conductor 44, to battery 32, and ground. At the same time a circuit willbe closed from ground, contact of jack J, upper contact of key Kconductor 45, winding of relay 29, conductor 46, to battery 32, andground. The closing of these two circuits will operate the relays 9, 26and 29. Theoperation of relay 29 will apply battery to the repeaterapparatus 12 over the following circuit: from ground, battery 31,contact of jack 5,, conductor 47, contact and armature of relay 29,filament of ballast lamp 30, over conductor 21, to the repeaterapparatus. The closing of this circuit will render the repeaterapparatus 12 in a condition for opemes oration. The operation of relay 9will connect the input circuit of repeater 12 to the induction coil ofsubstation 1 and the op-' eration otrelay 26 will connect the outputcircuit of repeater 12 to the receiver of substation 1. Accordingly, thecurrent comingin over conductors 7 and 8 to the substation will now betransmitted over con ductors 36 and 39 and over contacts and armaturesof relay .9 through the left hand winding of transformer 11. Thiscurrent will then be transmitted over conductors 18 and 19 to therepeater 12 and will be transmitted in amplified form therefrom overconductors 20 and 21. This current will be transmitted from conductor 21through the left hand winding of transformer 23 as follows: from.conductor 21, right hand normal contact of relay 22, conductor a8,series resistance 25, conductor 49, left hand windings of transformer23, conductor 50, to conductor 20. Bridged across this circuit is theshunt resistance 24. The shunt resistance 2e and the series, resistance25 are so proportioned as to regulate the gain of the repeater to adesired degree. The amplified current will then be transmitted throughthe transformer 23 and over condoctors 52 and 53, armatures and contactsof relay 2G, and over conductors 54 and 41, to the receiver 3. If theoperator upon supervising on a connection completed as describedascertains that the repeater is not giving thedesired degree ofamplification, the repeater may be adjusted so as to give a greatergain. This is accomplished by throwing the key K The throwing of key K,closes the following circuit from ground, contact of jack J, lowercontact ofkey K conductor 55, winding relay .22, to battery and ground.The closing of this circuit will operate the relay 22. At the same timeground will be applied from the upper contact of key K, to conductor 42and the previously traced circuit through relays 9 and 26 will be heldclosed. The operation of relay 22 will disconnect the shunt resistance24 and the series resistance 25 from the output circuit of repeater 12and the output circuit of repeater 12 will now be completed as follows:from conduc- -.tor 21, right hand make contact and arma-;

ture of relay 22, left hand windings of transformer 23, conductor 50, toconductor 20. The removal of these resistance elements from the outputcircuit of the repeater will increase the volunu: of sound in thereceiver 3-. It is pointed out that the repeater ape paratus cannot beconditioned for operation or connected to the substation by the oeration of either the key K, or the key a until a plug such as the plugof the operator: cord circuit or of the calling line has been insertedin the jack J and ground applied to the upper contact thereof. Thisarrangement serves as a safeguard to prevent the arrangements fromfunctioning until a con nection has been made with the substation.

While the invention has been disclosed as embodied in certain specificarrangements which have been deemed desirable, it is understood that itis capable of embodiment in many and widely varied forms withoutdeparting from the spirit of the invention as defined in the appendedclaims.

What is claimed is:

1. In a telephone system, a substation including a side tone reductioncoil and a receiver circuit, an amplifier associated with saidsubstation, a plurality of switching means, means controlled by each ofsaid switching means for including said amplifier in said receivercircuit, means controlled by each of said switchingameans for renderingsaid amplifier operative, and means controlled by one of said switchingmeans for increasing the gain of said amplifier.

'2. In a telephone system, a substation including a side tone reductioncoil and a receiver circuit, an amplifier associated with said receivercircuit, and a shunt across the input path of said amplifier, said shuntincluding an element the resistance of which name to this specificationthis 15th day of v May 1919.

' JOHN F. TOOMEY.

